It is well-known that a large amount of paper is produced from natural cellulosic pulp. Also, it is known that artificial paper-like sheets produced from various synthetic polymer materials are used as electric insulating sheets due to the excellent heat resistance and electric insulating property thereof. The most important electric insulating sheets are those comprising, as a principal component, an aromatic polyamide material, because the aromatic polyamide exhibits an excellent heat resistance. For example, Japanese Patent Application Publication (Kokoku) No. 43-20421 (1968) discloses an artificial paper-like sheet made from a mixture of mica particles and fibrids of an aromatic polyamide material which are substantially not melted and which are entangled with each other and with the mica particles, which sheet is useful as an electric insulating sheet having an excellent heat resistance. However, the conventional aromatic polyamide paper-like sheets are unsatisfactory not only in heat-resistance, for example, dimensional stability at an elevated temperature, but also, in the electric insulating property, for example, dielectric breakdown strength.
Under the above-mentioned circumstances, it is strongly desired to provide an aromatic polyamide paper-like sheet having excellent heat resistance and electric insulating properties.